SpaceX took its reusable Grasshopper rocket for another hop last week at the South by Southwest festival in Texas.

SpaceX CEO Elon Musk was there to demonstrate the Grasshopper's fourth test flight, which was twice as high as the reusable rocket has ever gone in previous demonstrations.

"Grasshopper touched down with its most accurate thus far on the centermost part of the launch pad," said SpaceX. "At touchdown, the thrust-to-weight ratio of the vehicle was greater than one, proving a key landing algorithm for Falcon 9."

The Grasshopper lifted to 24 stories (262.8 feet) off the ground, hovered for about 34 seconds and then landed safely back on the ground.

The Grasshopper is a Falcon first stage with a landing gear that's capable of taking off and landing vertically. It does this by shooting into orbit, turning around, restarting the engine, heading back to the launch site, changing its direction and deploying the landing gear. The end result is a vertical landing.

The reusable rocket was tested in September, November, December and last week Thursday.

Yes, I am aware of the three engine decent and return to launch site plan. My original comment was not so much pessimistic as cautious. I am hopeful that return to the launch site can be achieved, but even an intact landing up range would be an enormous benefit. You are quite correct that an equatorial launch to equatorial orbit would make return to launch site relatively trivial, but mainland USA is not so conveniently located. This means a trip of several hundred miles back down range from an altitude of say 120-130miles. The standard Cape launch trajectory to the ISS is northeast, which means alot more fuel is needed to return directly to Florida. I'm not saying they can't do it, just that an intact landing elsewhere would still be a huge a incredibly useful achievement.

As you may have seen from the latest launch, the first stage tends to fall immediately vertically and then sideways, aerodynamically belly-flopping on the atmosphere. The trick is to keep the stage vertical so that the engines can be used to slow the decent enough to maintain acceptable temperatures and structural stresses. Therefore, the cross-range return to launch site is purely a factor of engine vectoring. In contrast, Dragon has some small but useful amount of usable aerodynamic lift, so that fuel is mainly used for descent control rather than transverse manoeuvring. I suspect the second stage will be the most difficult, since it needs ablative shielding and will have to turn around in the atmosphere at high speed; something that Dragon does not need to do.

"Ablate" doesn't mean disintegrates; it is a method whereby the top layer(s) of the heat-shield "burns" and the exhaust gasing from the burning creates a pressure zone above the surface of the heatshield. So the greatest atmospheric friction temperatures are at the boundary of the outgasing whilst the actual heatshield below remains at a manageable temperature. The "ablative" material can theoretically survive multiple uses; tens, perhaps hundreds. Worst case, a heatshield refit every couple of dozen flights would be well within the realms of an acceptable maintenance regime.

Apparently, the plan is to do away with solar panels and instead rely on batteries for electrical power - don't know about cooling though. So the Dragon "trunk" becomes only an unpressurised cargo storage if and when needed and as such the cost of that part should be quite low - similar to the disposed nose cone. Unless of course Dragon 2/Rider is radically different to the present Dragon.